A materials handling vehicle is known having a first manifold located on a power unit and a second manifold located on a fork carriage apparatus, which, in turn, is mounted to a mast weldment. The first manifold includes “meter in” valve structure that controls the flow rate of a pressurized working fluid to the second manifold. Fluid supply and return lines extend between the first and second manifolds, i.e., from the power unit, along a mast assembly including the mast weldment to the fork carriage apparatus. To effect operation of an auxiliary device, e.g., a reach mechanism, a side-shift mechanism or a tilt mechanism, forming part of the fork carriage apparatus, an operator generates a command causing the valve structure within the first manifold to open to allow flow to travel to the second manifold, wherein the flow rate varies based on the selected auxiliary device and the magnitude of the operator input command Because the pressurized fluid is supplied at a constant flow rate corresponding to an operator-generated command from the first manifold, through the supply line between the first and second manifolds, to the second manifold, and from the second manifold through a further supply line to the desired auxiliary device, there is a delay from when the operator command is initiated until the supply line is expanded/filled with oil and sufficient fluid pressure is provided at the auxiliary device to effect operation of the auxiliary device.
Pressure controlled counterbalance valves are provided in the second manifold and are associated with the auxiliary device cylinders for receiving outgoing flow and function to create back pressure within the cylinders to allow the pistons within the cylinders to have a smooth motion. A counterbalance valve is required on both sides of a piston to lock it into place. When operating the circuit, the counterbalance valve in the supply side of the circuit will have flow passing through its check valve. The counterbalance valve on the return side of the circuit is creating the backpressure to control any over running load that may exist. When a stop command is issued, the counterbalance valve creating the backpressure will close when the pressure conditions in the circuit are below the pressure required to hold the valve open. The piston is then locked in place. The reach circuit has two pistons operating in parallel. Both pistons are locked by the same valves. Counterbalance valves increase system pressure; hence, a larger volume of oil is required to fill the supply line extending between the first and second manifolds due to expansion of the hoses. This large volume of oil causes a delay between when an operator initiates either a start or a stop command and operation of the corresponding auxiliary device is either started or stopped. Because the counterbalance valves are pressure controlled, a counterbalance valve only closes after the fluid pressure in a corresponding line falls below the counterbalance valve threshold. Hence, movement of the piston within the corresponding auxiliary device cylinder continues after a stop command has been initiated until the pressure falls below the threshold required to close the corresponding counterbalance valve, thereby resulting in a delay before the auxiliary device stops.